Vinyl chloride resins and plasticizers therefor stabilized with 1, 1-bis (2-methyl-5-tertiary butyl-4-hydroxyphenyl) butane



United States Patent 3,384,608 VINYL CHLORIDE RESINS AND PLASTICIZ- ERSTHEREFOR STABILIZED WITH 1,1-BIS (2 METHYL 5 TERTIARY BUTYL 4 HY-DROXYPHENYL) BUTANE George F. Hardy and Ronald Saltzman, Madison, N.J.,assignors to Allied Chemical Corporation, New York, N.Y., a corporationof New York No Drawing. Filed Aug. 7, 1964, Ser. No. 388,305 4 Claims.(Cl. 260-313) This invention relates to stabilized ester plasticizersand to vinyl resin compositions of improved electrical resistancecharacteristics containing such stabilized esters.

Organic esters of dicarboxylic acids useful as plasticizers forpolyvinyl chloride resin compositions are well known. In the preparationof plasticized polyvinyl chloride insulating compositions, phthalicesters of C to C chain alcohols are especially useful. These includedi-2- ethylhexyl phthalate, diisodecyl phthalate, dioctyl phthalate,diisooctyl phthalate, ditridecyl phthalate, etc. A primary utility ofsuch plasticizers is in blending with polyvinyl chloride for theproduction of wire insulating com positions. Such compositions areapplied as coatings around the wires, usually by extruding the softenedcoating composition around an advancing core of wire at elevatedtemperatures of about 150 C.

One of the most valued characteristics of a wire coating besides itsmechanical effectiveness is the electrical resistance of thecomposition, and improvement of this characteristic is an object ofcontinuing effort by suppliers and user of such coatings. Electricalresistance of a coating may be evaluated as volume resistivity by thestandard ASTM Test Method D-257-58 from measurements of volumeresistance of the coating.

Especially suitable as plasticizers in the preparation of polyvinylchloride insulating compositions are phthalic acid esters prepared frombranched chain alcohols obtained by the so called oxo process wherein anolefin feed is reacted with carbon monoxide and hydrogen at temperaturesbetween about 250 F. and 400 F. and pressures of about 150 to 400atmospheres in the presence of suitable catalysts, and the aldehydes soformed are hydrogenated to form alcohols. Such oxo alcohols are in the C-C range and these alcohols, especially those in the C -C range, areespecially useful in forming esters such as the phthalic esters, for useas plasticizers in insulating plastics and resins.

In spite of the desirable properties and mechanical effectiveness of thepolyvinyl chloride resins plasticized with such ester plasticizers,their utility in insulating compositions has been limited by theinstability of the plasticizers during storage and prolonged aging andin their end uses combined with polyvinyl chloride resins in electricalinsulating applications.

An object of the present invention is to provide phthalic acid diestersof C -C alcohols, including the branched chain 0x0 alcohols, having ahigh degree of stability against oxidative degradation on prolongedstorage.

Another object of the invention is to provide polyvinyl chloride resincompositions plasticized with C C diesters of phthalic acid havingimproved electrical resistance properties.

These and other objects are accomplished according to our inventionwherein the stability of the phthalic acid ester plasticizer isprolonged, and the volume resistivities of polyvinyl chloride resincompositions plasticized therewith are enhanced by the addition to saidplasticizer ester of small quantities of 1,l-bis-(Z-mcthyl-5-tertiarybutyi-4- hydroxyphenyl) butane of the formula:

"ice

The above compound, sometimes called 4,4-butylidenebis-(6-tert-butyl-m-cresol), is a white solid obtainable commercially inpowdered form.

In preparing the stabilized plasticizer esters and resulting stabilizedvinyl resin compositions of our invention, small amounts, for examplebetween about 0.05 part and about 0.20 part by weight of the solid1,1-bis-(2- methyl-S-tertiary butyl-4-hydroxyphenyl) butane are mixedwith parts of the liquid plasticizer in any suitable manner, as in anagitated blending tank and stirred until the stabilizer dissolves in theplasticizer.

The plasticized vinyl resin compositions may be prepared in conventionalmanner as by dry blending resin, plasticizer and filler components andmilling the mixture on a heated roller mill or in a dough mixer untilthe components are thoroughly blended.

Plasticizers which are adapted for stabilization according to ourinvention are the straight chain and branched chain C -C alkyl andcycloalkyl esters of phthalic acid and especially the C -C alkyl andcycloalkyl esters, including dioctyl phthalate, diisooctyl phthalate,diisodecyl phthalate, di-Z-ethylhexyl phthalate, ditridecyl phthalate,and dicyclohexyl phthalate.

Addition to the above plasticizers of the small proportions ofl,l-bis-(2-methyl-5-tertiary butyl-4-hydroxyphenyl) butane indicated,fully stabilizes the plasticizer for substantial storage periods and,when the stabilized plasticizer is blended with polyvinyl chlorideresins, provides compositions not only of improved stability, but ofgreatly enhanced volume resistivity as compared to similar compositionscontaining no stabilizer.

While 1,l-bis-(Z-methyl-S-tertiary butyl 4-hydroxyphenyl) butane may beused as the sole stabilizer in the compositions of our invention, wefind that the addition to the stabilized plasticizer of between about0.2 part and about 0.5 part per 100 parts of plasticizer by weight, of aphosphite ester such as triphenyl phosphite or a diphenyl, mono-alkylphosphite, further improves the volume resistivity of polyvinyl chlorideresin compositions containing these plasticizers, often by as much as50% to 100%. Other conventional additives may also be included.

The phosphite esters suitable for combination with1,1-bis-(Z-methyl-S-tertiary butyl-4-hydroxyphenyl) butane in ourstabilizer system have the formula shown below:

wherein R is a member selected from the group consisting of hydrogen,alkyl radicals of l-lO carbon atoms the phenyl radical, and 1-10 carbonatom alkyl-substituted phenyl radicals, R and R are members selectedfrom the group consisting of alkyl radicals of 1-10 carbon atoms, thephenyl radical and l-lO carbon atom alkyl-substituted phenyl radicals.Particularly effective are: triphenylphosphite; tris (nonylphenyl)phosphite; Z-ethylhexyl, octyl phenylphosphite; tris (2 ethylhexyl)phosphite; and di (2-ethylhexyl)-hydrogen phosphite.

The stabilized esters of our invention are particularly useful in vinylresin formulations which employ calcium carbonate as a portion or all ofthe filler content since such compositions are not susceptible ofadequate stabilization by many of the prior art stabilization systems.

Plasticizer proportions used in compounding electrically resistivecompositions are those conventionally employed for this purpose and, inthe case of polyvinyl chloride resin compositions, usually range betweenabout 50 parts and about 100 parts of stabilized plasticizer per 100parts of polyvinyl chloride resin by weight. Conven tional fillers mayalso be employed, as well as other common additives such as lubricants,additional stabilizers, etc.

By the term vinyl chloride resin is meant vinyl chloride polymers andvinyl chloride copolymers wherein the vinyl chloride is copolymerizedwith other ethylenically unsaturated compounds, the said copolymerscontaining a major proportion by weight of vinyl chloride. Ethylenicallyunsaturated compounds which can be copolymerized with vinyl chlorideinclude the vinylidene halides such as vinylidene chloride andvinylidene bromide; vinyl esters such as vinyl acetate, vinylpropionate, etc.; acrylic acid, alpha alkyl acrylic acids, their alkylesters, etc.

The following specific examples further illustrate our invention. Partsand percentages are by weight except as otherwise noted.

EXAMPLES 1 AND 2 tiary butyl-4-hydroxy-phenyl) butane and 0.2% oftriphenyl phosphite.

In carrying out the tests, a five ml. sample (4.5 grams) of thestabilizer-containing diisodecyl phthalate was placed at the bottom of a50 ml. volumetric flask, providing a depth of plasticizer of 0.5 cm. Asmall glass wool plug was placed at the bottom of the neck of the flask,and the remainder of the neck was filled with Molecular Sieve, type 5Apellets, i.e. calcium zeolite pellets, pore size about 5 Angstroms. Thetop of the neck was connected to a U-tube and the flask was evacuated to1 mm. Hg and then filled with dry nitrogen. This evacuation and nitrogenfilling was repeated three times. Then the flask was lowered into a 151C. silicone oil bath, and was allowed to remain therein for 4.5 minutesto equilibrate temperature of gas inside the flask with that of thebath. The flask was then evacuated to 1 mm. Hg for 0.5 minute, thenfilled with USP oxygen. After one minute (zero time being taken at themoment the oxygen was admitted) the apparatus was sealed off. Then thevolume of oxygen absorbed was measured periodically by leveling mercuryin both arms of the U-tube and noting the height of mercury column inthe arm attached to the flask. Measurernents were taken for three hours.A- blank with no ester gave no detectable oxygen absorption. Results areshown in Table I below.

Table I EFFECT OF STABILIZERS ON RATE OF OXIDATION OF DIISODECYLPHTHALATE Oxygen obsorption rate,

Stabilizer 103 X cc./ g./ min. None 492 Ex. 1, 1,1-bis- 2-methy-5-tertiary butyl-4-hydroxyphenyl) butane (0.1%) 3.0

Ex. 2, 1,1-bis (Z-methyl-S-tertiary butyl-4-1ydroxyphenyl) butane andtriphenyl phosphite (0.2%) 1.3

Bisphenol A (ca. .25%) s.. 5.2

4 EXAMPLES 3-6 Four standard vinyl resin formulations of thecompositions given below were prepared.

Parts by weight Polyvinyl chloride Plasticizer-i-stabilizer 60 Clay -l-21 Calcium carbonate 15 Lead silicate/sulfate 5 tearic acid 0.25

In each formulation, the plasticizer wasdiisodecyl phthalate modified bythe addition of stabilizer listed below.

Example No.: Stabilizer 3 0.2% 1,1-bis-(Z-methyl-S-tertiary-butyl-4-hydroxyphenyl) butane. 4 0.05% l,l-bis-(Z-methyl-S-tertiary-butyl-4-hydroxyphenyl) butane. 5 0.05 1,1-bis-(2-methyl-5-tertiary-butyl-4-hydroxyphenyl) butane, 0.25% triphenyl phosphite. i 6 0.05l,l-bis-(2-methyl-5-tertiary-butyl- 4-hydroxyphenyl) butane, 0.5%triphenyl phosphite. No added stabilizer. 0.2% Bisphenol A.

The separate formulations were dry blended and milled on a standard tworoll mill at about 300 F. and were sheeted oil at thicknesses of 2025mils. Specimens were cut and subjected to volume resistivitydeterminations at 70 C. using 500 volts for one minute according to ASTMTest Method D-257-58. Three specimens of each sample were measured.Results are shown in Table'll below.

Control A Control B Compound volume resistivity,

Example No.: ohm-cm. X 10 3 77 4 55 5 96 6 122 Control B (0.2% BisphenolA) 2.7

wherein R is a member selected from the group consisting of hydrogen,the phenyl radical, 1-10 carbon atom alkyl substituted phenyl radicals,and alkyl radicals of 1-10 carbon atoms, R and R are selected from thegroup consisting of the phenyl radical, 1-10 carbon atoms substitutedphenyl radicals, and alkyl radicals of 110 carbon atoms.

2. The plasticizer composition of claim 1 in which the organic phosphiteis triphenyl phosphite.

3. A wire coating composition of high volume resistivity comprising: (A)a .vinyl chloride polymer selected from the group of polyvinyl chlorideand copolymers of a major portion of vinyl chloride with a minor portionof a monoethylenica lly unsaturated monomer copolymer- 5 izable withvinyl chloride; (B) calcium carbonate as filler; (C) diisodecylphthalate prepared from 0X0 prepared alcohol; and (D) between about0.05% to 0.2% by weight of 1,1-bis(2-methyl-5-tertiarybutyl-4-hydroxyphenyl) butane and between about 0.2% to 0.5% by weightof an organic phosphite of the formula:

R O-P 0R wherein R is a member selected from the group consisting ofhydrogen, the phenyl radical, 1-10 carbon atom alkyl substituted phenylradicals, and alkyl radicals of 1-10 carbon atoms, R and R are selectedfrom the group consisting of the phenyl radical, 1-10 carbon atomssubstituted phenyl radicals, and alkyl radicals of 1-l0 carbon atoms,said percentages based on the weight of said diisodecyl phthalate.

4. The wire coating composition of claim 3 in which the organicphosphite is triphenyl phosphite and in which the filler is acombination of clay and calcium carbonate.

6 References Cited UNITED STATES PATENTS 2,675,366 4/1954 Pullman260-4595 2,919,259 12/1959 Naylor et a1 260-4595 3,091,597 5/ 1963Henriques 260-4595 3,225,001 12/1965 Darsa 260-31.8 3,012,009 12/1961Martin 117-1284 FOREIGN PATENTS 1,149,359 5/1963 Germany.

OTHER REFERENCES Penn: PVC Technology; MaClaren & Sons, Ltd.; 1962;pages 147-148.

Murfitt: Antioxidants for Stabilizing Plasticized P.V.C.; BritishPlastics; vol. 33; December 1960; pages 578-581.

MORRIS LIEBMAN, Primary Examiner.

L. T. JACOBS, Assistant Examiner.

1. A PLASTICIZER COMPOSITION STABLE AGAINST OXIDATIVE DEGRADATION WHICHCOMPRISES DIISODECYL PHTHALATE PREPARED FROM "OXO" PREPARED ALCOHOLHAVING DISSOLVED THEREIN THE COMBINATION OF BETWEEN ABOUT 0.05% TO 0.2%BY WEIGHT OF 1,1-BIS(2-METHYL-5-TERTIARY BUTYL-4- HYDROXYPEHNYL) BUTANEAND BETWEEN ABOUT 0.2% TO 0.5% BY WEIGHT OF AN ORGANIC PHOSPHITE OF THEFORMULA:
 3. A WIRE COATING COMPOSITION OF HIGH VOLUME RESISTIVITYCOMPRISING: (A) A VINYL CHLORIDE POLYMER SELECTED FROM THE GROUP OFPOLYVINYL CHLORIDE AND COPOLYMERS OF A MAJOR PORTION OF VINYL CHLORIDEWITH A MINOR PORTION OF A MONOETHYLENICALLY UNSATURATED MONOMERCOPOLYMERIZABLE WITH VINYL CHLORIDE; (B) CALCIUM CARBONATE AS FILLER;(C) DIISODECYL PHTHALATE PREPARED FROM "OXO" PREPARED ALCOHOL; AND (D)BETWEEN ABOUT 0.05% TO 0.2% BY WEIGHT OF 1,1-BIS(2-METHYL-5-TERTIARYBUTYL-4-HYDROXYPHENYL) BUTANE AND BETWEEN ABOUT 0.2% TO 0.5% BY WEIGHTOF AN ORGANIC PHOSPHITE OF THE FORMULA: